None, I use copper gaskets installed on clean and dry surfaces. Then torque to 45 foot pounds and check several times after engine has heated and cooled.
If I use something other than a copper gasket, I will coat it with Copper Coat. CC stays pliable and gives an added seal. I don't measure the torque on manifold bolts; I just tighten them till they feel right. But I do retorque them as Al suggests.
